Traumatic brain injury (TBI) in children has serious neurobehavioral consequences and is a leading cause of lifelong disability. Despite concern that the social deficits following TBI may be more debilitating than the cognitive and physical consequences, minimal research has focused on social outcomes and no research has directly assessed relationships with peers. Social competence with peers requires successful social interactions, abilities to develop and sustain friendships, and acceptance into peer groups. Long-term social competence with peers and others following TBI has particular relevance for young children, yet this age group has been neglected in TBI outcome research. Development of social competence during the preschool and the early school-age years has been linked to later academic success and emotional well-being. Due to the timing and nature of the insult to the brain, children suffering TBI during the preschool years are at high risk for deficits in the neuropsychological abilities that lay the foundation for social information processing skills and influence social behavior and adjustment. Research on social outcomes following pediatric TBI has not kept pace with theoretical and methodological advances made in the field of developmental psychology regarding the development of social competence with peers. Our research group is currently conducting two integrated NIH-funded studies of child and family outcomes of TBI. The current application seeks funding to expand our investigation by evaluating social competence with peers during the early school years (2nd through 4th grade) in children who were originally injured between 3-6 years of age (and are therefore at least 18 months post- injury). The study will be the first prospective study of later adjustment with peers. We propose to follow at least 30 children with TBI and 30 children with orthopedic injury (OI) using a classroom-based assessment of social competence with peers. We hypothesize that children with a history of TBI will demonstrate deficits in peer interactions, relationships, and group acceptance relative to children with a history of OI. We will explore the linkages between neuropsychological abilities, social information processing skills, and later peer relationship outcomes in children with a history of TBI. We will also begin to explore injury severity and family factors that may influence social competence with peers. The study utilizes a well-developed theoretical framework and the associated classroom-based methodology drawn from the field of developmental psychology. Findings will inform the development of interventions to improve peer relationships after TBI. Development of social competence during the preschool and the early school-age years has been linked to later academic success and emotional well-being. Failure to understand social outcomes following early childhood TBI impedes our ability to develop empirically-supported interventions that have the potential to impact a child's quality of life, academic achievement, and emotional adjustment following TBI.